Key Message

This core indicator evaluates the average concentration of dissolved inorganic phosphorus (DIP) in surface waters (0 – 10 m) during winter (December – February) for the assessment period 2011-2016.

Of the 17 open-sea sub-basins, good status (DIP concentration below defined threshold value, which reflects good conditions) was only achieved in the Bothnian Bay (Key message figure 1). Of the remaining 16 sub-basins: the Kattegat, Great Belt and Kiel Bay were close to their respective threshold values (ER < 1.2), whereas the remaining basins were distant from the threshold values (Results table 1). Of all coastal waters that were assessed, good eutrophication status was only found in some areas of the Swedish and Polish coastal waters (Key message figure 1).

The confidence of the presented DIPstatus estimate was high only in the Kattegat, Arkona and Bornholm Basin. Confidence in other assessed open sea areas was either moderate or low (see below).

The indicator is applicable in the waters of all countries bordering the Baltic Sea. In coastal waters, total phosphorus may have been assessed instead of DIP (see Total Nitrogen indicator report) in line with the national assessments under the Water Framework Directive and the Russian Maritime Doctrine.

Relevance of the core indicator

Eutrophication is caused by excessive inputs of nutrients (nitrogen and phosphorus) resulting from various human activities. High concentrations of nutrients and the ratios of these nutrients (e.g. N:P stoichiometric ratios) form the preconditions for algal blooms, reduced water clarity and increased oxygen consumption. Long-term nutrient data are key parameters for quantifying the effects of anthropogenic activities and evaluating the success of measures undertaken.

Policy relevance of the core indicator

BSAP Segment and Objectives

MSFD Descriptors and Criteria

Primary link

Baltic Sea unaffected by eutrophication

D5 Human-induced eutrophication

- D5C1 Nutrient concentrations are not at levels that indicate adverse eutrophication effects